Electric discharge lamp



' A. H. WILLOUGHBY ELECTRIC DISCHARGE LAMP July 24, 1951 Filed April 5, 1949 w u F m m eH w o n .A

Patented July 24, 1951 ELECTRIC DISCHARGE LAMP Anthony Haydn Wiiloughby, Carston, warm, England, assignor to General Electric Company, a corporation of New York Application April 5, 1949, Serial No. 85,504- In Great Britain May 13, 1948 v Claims.

This invention relates to' electric discharge lamps generally, and more particularly to lamps of the type wherein in normal operation the pressure of the gas or vapor filling is not less than mms. of mercury and which include within .the sealed vitreousenvelope of the lamp an unsealed transparent or translucent irmer tube which is of material more refractory than the envelope and which extends between two electrodes so as to contain the discharge between these electrodes in normal operation of the lamp. The inner tube in general constricts the discharge and provides a bright light source for cooperation with optical apparatus.

i In such lamps it is found that the inner tube tends to become rapidly obscured by the deposition o'n'it of metal sputtered from .the electrodes and the eiliciency of the lamp is thereby quickly impaired. An. object of this invention is to reduce this difllculty.

- According tothe invention an electric discharge lamp of.-the type specified comprises, in the neighborhood of at least one of said electrodes,

. baflle means arranged so as to screen at least the greater part of the irmer surface of the said inner tube from the corresponding electrode.

Metal sputtered from the said electrodes which would have been deposited on the inner surface of the tube is thus intercepted by the battle means and prevented from reaching the tube. The said baflle means are preferably of the same material as the .inner tube and sealed to or integral with it. Preferably the said material is quartz and the sealed envelope of the lamp is of glass.

The said baille means-are preferably positioned outside and extend across the ends of the inner tube so as to leave gaps for. the passage of the discharge,'for example, the means may consist of battle discs positioned across the ends of the inner tube, being attached to the ends at spaced points, or thebaflle means may be integral with the tube and consist of domes across the ends of the inner tube, each dome having one or more apertures to provide a path for the discharge therethrough.

In one preferred form of this invention an electric discharge lamp has the baille means outside and extending across the ends of the inner tube and this inner tube is provided, near its ends. with expanded end members which extend from the outer surface of the inner tube and which surround the baflle means and also extend around the electrodes. These expanded end members are also preferably of the same material as the inner tube, e. g. of quartz.

through the outer vitreous envelope and-projects intothe discharge path through the wall of the said inner tube at a point between the electrodes, preferably the auxiliary electrode is sheathed throughout all of its length between the inner 7 tube and the envelope by vitreous material 'so as to minimize the possibility of the discharge striking outside the inner tube.

One electric discharge lamp in accordance with the invention will now be described in detail by way of example, namely, an electric discharge flash lamp of the type suitabfe for stroboscopic purposes and adapted for. operation on direct current. In" the drawing, Fig. l is an elevation, in section of such a lamp, and Fig. 2 is a partial sectional view of a modification.

The lamp comprises a hermetically at a pressure of about half an atmosphere; the envelope has sealed through it at each tungsten rod electrodes 2 and 3 one of which (3) is activated to act as cathode and the other of which (2) serves as anode. A cup or tab 4 for supporting a getter is attached to the cathode, and the parts of the electrode rods outside the envelope may be welded to nickel tubes (not shown) which may be in turn soldered to metal caps (not shown) which act as terminals for the lamp. A quartz inner tube 5 of substantially smaller diameter than the envelope l extends between, but not touching, the electrodes so that its axis is roughly If the lamp comprises an auxiliary electrode for starting purposes, which electrode is sealed collinear with the axis of the electrodes. This inner tube 5 is constructed with quartz baille discs 6 of substantially the same area of cross section as the open ends of the said inner tube. each of which baflie discs is rigidly attached to the periphery of the corresponding and of the tube 5 by two narrow quartz straps?! so as to leave gaps between the peripheries of the :said ends of the inner tube 5 and the baille discs C, through which gaps the discharge is adapted to pass. The inner tube 5 and the baflle discs 6 are thus so positioned and dimensioned that each baflle disc screen the inner surfa e of the tube from the corresponding electrode. Bulbous quartz members 8 and 9 are sealed to the outer surface of the inner tube 5 near its ends and extend near the ends of the envelope I and around the elec trodes 2, 3, one fitting closely around the anode 2 and the other more loosely around the cathode 3 to permit the insertion of the cathode l and the getter; cup 4 in manufacture, but fitting closely around'the inner wall of the envelope.

A tungsten auxiliary electrode III is sealed through the envelope l at approximately the mid point of the length of the envelope and passes sealedtubu- 'lar glass envelope I having'a gas filling orargon through an aperture II in the wall of the inner tube I. This electrode II is sheathed with glass II for all of its length within the lamp envelope, except for the extreme tip lying inside the inner tube I; a suitable terminal cap I! is provided on the part of the electrode ll outside the envelope.

The body formed by the inner tube 5, the baille discs 6 and the bulbous ends 9, 9 rests loosely around and between the electrodes 2 and 3, being constrained from violent movement by the said electrodes and the glass sheath I! of the auxiliary electrode II. which sheath I2 flts closely into the said aperture II' in the wall of the inner tube.

In a modification of this embodiment shown in Fig. 2, the lamp is constructed similarly except that the baflle means consist of domes l4 instead of discs, the domes being formed on the edges of and integral with, so as substantially to close, the inner tube 5, each dome having two apertures Ii in its wall to form a passage for the discharge. In manufacture these apertures l5 are blown through the domes ll before the bulbous members l and 9 are sealed to the inner tube.

What I claim as new and desire to secure by Letters Patent of the United State is:

a 1. An electric discharge lamp comprising a sealed vitreous envelope containing a gaseous ionizable medium having a pressure during normal operation of the lamp not less than 10 mm., a pair of electrodes and an inner tube or substantially smaller diameter than said envelope and of light-pervious material more refractory than said envelope and extending between said electrodes, means to confine the discharge between said electrodes during operation of the lamp to a path through the interior of said tube, and ballle means interposed between at least one of said electrodes and the adjacent end of said tube to intercept material sputtered from the electrode.

2. An electric discharge lamp comprising a sealed vitreous envelope containing a gaseous ionizable medium having a pressure during normal operation of the lamp not less than 10 mm., a pair of electrodes and an inner tube of substantially smaller diameter than said envelope and of light-pcrvious material more refractory than said envelope and extending between said electrodes, means to confine the discharge between said electrodes during operation of the lamp to a path through the interior of said tube, and baifle discs interposed between each of the respective electrodes and the adjacent end of said tube and disposed across the ends of said tube but spaced therefrom to intercept material sputtered from the electrodes.

3. An electric discharge lamp comprising a sealed vitreous envelope containing a gaseous ionizable medium having a pressure during normal operation of the lamp not less than 10 mm., a pair of electrodes and an inner tube of substantially smaller diameter than said envelope and of light-pervious material more refractory than said envelope and extending between said electrodes means and also extends around the adjacent electrode to confine the discharge to a path through the interior of said tube.

4. An electric discharge lamp comprising a sealed vitreous envelope containing a gaseous ionizable medium having a pressure during normal operation of the lamp notless than 10 mm., a pair of electrodes and an inner tube of substantially smaller diameter than said envelope and of light-pervious material more refractory than said envelope and extending between said electrodes so as to contain the discharge between said electrodes during operation of the lamp, and heme discs interposed between each of the respective electrodes and the adjacent end of said tube and disposed across the ends of said tube but spaced therefrom to intercept material sputtered from the electrodes, the ends of said tube being provided with expanded end members which surround the respective ballle means and also extend around the respective electrodes to confine the i discharge to apath through the interior of said tube.

5. An electric discharge lamp comprising a sealed vitreous envelope containing a gaseous ionizable medium having a pressure during normal operation of the lamp not less than 10 mm., a pair of electrodes and an inner tube of substantially smaller diameter than said envelope and of light-pervious material more refractory than said envelope and extending between said electrodes, means to confine the discharge between said electrodes during operation of the lamp to a path through the interior of said tube, and baille means interposed between at least one of said electrodes and the adjacent end of said tube to intercept material sputtered from the electrode, and an auxiliary electrode sealed through said envelope and projecting into the discharge path through an aperture in the wall of said inner tube, said auxiliary electrode being sheathed with insulating material throughout its length between the inner tube and the envelope.

ANTHONY HAYDN WILLOUGHBY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,958,239 Found May 8, 1934 1,984,483 Kenty' Dec. 18, 1934 2,025,934 Brett Dec. 31, 1935 2,030,450 Haucke Feb. 11, 1936 2,087,735 Piranl July 20, 193'! 2,351,616 Karash June 20, 1944 Certificate of Correction Patent No. 2,561,898 July 24 1951 ANTHONY HAYDN WILLOUGHBY It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 18, for filling or read filling of line 20, after each insert end; line 37, for corresponding and read corresponding end; and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 15th day of January, A. D. 1952.

THOMAS F. MURPHY,

Assistant Oommz'ssz'oner of Patents. 

